Haze raises risk of cardiac arrest
STUDY finds that the regional problem raises the risk of cardiac arrest by as much as 30 per cent when the PSI enters the unhealthy range.
The misty grey curtain of smoke and smell of burning wood that makes a regular appearance, usually in the third quarter of the year, doesn’t just irritate throats, sting the eyes or cause breathlessness.
The haze from burning forests in the region can also cause people, especially the elderly, to suffer cardiac arrest, a study by Singapore General Hospital (SGH ) has found. Cardiac arrest occurs when the heart suddenly stops beating and the person collapses. Few people survive a cardiac arrest unless they get prompt attention, such as having cardiopulmonary resuscitation (CPR ) and/or the use of an automated external defribillator (AED ) to restart the heart.
According to Associate Professor Marcus Ong, Senior Consultant, Department of Emergency Medicine, SGH , the study found that the risk of cardiac arrest increased by 10 per cent when air quality was moderate, measured by the Pollution Standards Index ( PSI ) that Singapore’s National Environment Agency uses. When the PSI entered the unhealthy range, the risk of cardiac arrest increased by almost 30 per cent.
The rise in the number of cardiac arrest cases that followed a spike in the PSI lingered over a few days. “This lag effect (of a heightened risk of a cardiac arrest occurring) peaked between day 1 and 3 (of the rise in PSI ), and lasted at least five days,” said Prof Ong, who is also senior author of the study.
Older people were more vulnerable, with those at least 65 years of age having a 1.41 risk of cardiac arrest when the PSI was in the unhealthy range, compared to 1.27 for those below the age of 65.
As an ecological study, however, it doesn’t explain why the risk of cardiac arrest increases with a more polluted environment. “One theory is that when the air is bad, you have to work harder to breathe. That puts a bigger strain on the heart if you already have an underlying heart problem,” said Prof Ong.
While there may be multiple factors at play, he added, the results of the study provided “very strong scientific evidence” of a link between air pollution and a higher risk of cardiac arrest.
In recent years, the government has taken steps to improve survival in cardiac arrests that occur outside hospitals by having programmes that encourage more people to perform CPR and defibrillation.
These programmes include simplified CPR training for adults and children; dispatcher-assisted CPR, where trained 995 operators teach phone callers how to perform CPR; my Responder phone app for activating volunteer responders within 400m of a person who has collapsed from cardiac arrest; and more AED s.
These community programmes appear to have been effective, according to another study by Prof Ong. It found that the survival rate for out- of-hospital cardiac arrests in Singapore improved to 14 per cent in 2014 from 11 per cent in 2011. Bystander CPR rates (50 per cent in 2014 from 22 per cent
in 2011) and bystander AED use also increased ( 3.5 per cent from 1.8 per cent), the study said.
While the incidence of outof-hospital cardiac arrests is increasing in line with a rapidly ageing population, communitywide efforts are showing an impact, said Prof Ong. He cited bystander CPR, defribillation using an AED by a member of the public or a paramedic, and ambulance response
times as the three strongest factors that have contributed to more people surviving a cardiac arrest.
Some CPR better than no CPR
When cardiac arrest occurs, the blood flow stops – meaning the brain isn’t getting enough oxygen. When that happens, the vital organs start to die.
“The chances of survival decreases by 10 per cent for every minute that nothing gets done,” said Associate Professor Marcus Ong, Senior Consultant, Department of Emergency Medicine, Singapore General Hospital.
While performing CPR properly – pumping the chest down by 4cm to 5cm at 100 times per minute, among other steps – is best, having some CPR done is better than no CPR at all.
“If the bystander doesn’t do anything, the chance of survival is close to zero,” said Prof Ong.
“But doing something, even if it’s not- so- good CPR, buys the person who has collapsed some time before the ambulance arrives. And that helps.
“Data shows that people who get bystander CPR have a two times higher survival rate than those who don’t.”
• This story was first published in Singapore Health, Nov – Dec 2017 issue.